In fast service and carry-out food businesses, it is necessary to package food products in containers which are inexpensive, easy to ship and store, and convenient to use for the retailer and the consumer. When assembled and filled with food products, such containers must be easy to close and open, and yet they must remain shut in transport from the food counter to a table or other carry out location. It is also important, in the design and construction of such containers, to take into account environmental aspects of their use.
One form of packaging which has addressed these concerns, and has met with acceptance, is a carton comprised of a joined tray and cover with integral latching means which can be readily formed from a cut and scored blank. The cut and scored blank is made from paperboard, boxboard or corrugated board. When partially folded and glued, the blank forms a hingedly connected tray and cover, each in the form of a truncated pyramid. Such partially folded cartons can be shipped and stored in nested condition. In use, various food products, such as hamburgers, chicken pieces, pizza slices and the like, are placed in the tray portion of the partially folded carton, and the cover portion is folded over the tray portion and latched thereto at a location opposite the fold or hinge in the back panel of the carton. Such double cavity, folded tray and cover, cartons are referred to a clamshell cartons.
The design of a suitable latching mechanism for such clamshell cartons has been an object of prior art efforts. The latching mechanism must do more than simply keep the carton closed. It must be foolproof, simple and quick to use, positive and secure in its engagement, and so designed that it will not be prone to damage during transportation of the nested cartons or while being handled by restaurant crew persons or patrons.
A generally accepted prior art clamshell carton which features integral latching means is disclosed, for example, in U.S. Pat. No. 4,877,178, issued Oct. 31, 1989 to Dopaco, Inc. as assignee. In the Dopaco carton, two primary detents extend forwardly from slightly above the front wall of the tray portion. The detents are minimal in size and are double laminated during carton fabrication for additional stiffness, which enhances their performance and durability. Upon closing, the detents engage corresponding, triangular-shaped slots in each of the forward cover glue flaps.
While providing a tight and secure fit of the carton portions, the Dopaco latching mechanism has proven to be difficult to open. The natural tendency for the customer has been to pull on the center of the overhanging front panel of the cover portion to open the carton. However, this action draws the outside corners of the triangular-shaped slots into contact with the tray detents, preventing their release. Alternatively, the user can work with each corner of the carton to free the detents; this has proven cumbersome and equally ineffective. Furthermore, the triangular flaps that remain after the cover flap slots are cut in the Dopaco carton do not always pop out when the clamshell is formed and, thus, have been known to interfere with and delay closing of the carton.
Other prior art clamshell cartons have used cover engagement hooks formed from the front panel or side panels of the carton cover. The engagement hooks usually extend beyond the width or length of the carton, and suffer the disadvantage of being subject to damage during shipping and handling.
Accordingly, it is a primary object of the present invention to provide a clamshell carton having an improved latching means, which is simpler and more reliable in use.